Boltolomew lives the peaceful life of a cleaning robot on the distant, long forgotten planet of Greta, until the day he finds an old music box in his garage. He doesn't know what it is, but he can't take his CPU off it for a moment. When he shows it to his friends, they're just as puzzled.
The mysterious box is just the beginning of Boltolomew's troubles: soon he begins seeing a Spaceship landing on his way home from work, although no one else can see it, and then even stranger things start happening. One night, visitors emerge from the craft, only to vanish into thin air, leaving Boltolomew confused and overheated from too much thinking. Boltolomew's friends become concerned for him, and his Supervisor at the Cleaning Factory, Chief Bot, decides to have him reprogrammed.
Boltolomew doesn't want to be reprogrammed, however, because it would make him forget the things he saw - well, he's pretty sure that he saw them, anyway. He must make a difficult choice: stay in the City without any memory of his previous self, or run away and face the dangers of the desolate Junk Yard. But most of all, Boltolomew wants to know: who are the visitors from the Spaceship, and why can't anyone else see it?